The unexpected encountering of a concealed blood vessel in surgery can have disastrous results. For example, in conventional open heart transmyocardial revascularization (TMR) a channel is created through the heart wall from the outside to the inside of the left ventricle using a laser beam typically from a CO.sub.2 laser. The channel heals quickly on the outside from slight finger pressure so there is no substantial bleeding. The channel remains open on the inside part way through the heart wall so that the heart muscle is supplied with blood by suffusion through the channel from within the ventricle. With a number of such channels the blood supply to the heart muscle can be restored to ensure proper functioning of the heart despite occluded coronary arteries. One problem encountered in TMR is the danger of creating a channel in a path which cuts an unseen vessel in the heart wall. When this occurs substantial bleeding can occur so that a stitch will be required on the outside of the channel at the heart wall to stanch the bleeding. In addition to the obvious danger and extra effort required, this technique also results in a less extensive channel. That is, channels which have such a stitch tend to heal for a longer distance into the heart wall thereby shortening the channel where the blood flows and reducing that area of the heart muscle suffused.